Delayed-action fuse



March 1, 1949 B. w. SEWELL DELAYED-ACTION FUSE Filed April 15, 1947 2Sheets-Sheet 1 w mm w r J an m M F E: F m

' INVENTOR EEK! W. $EWEL v ATTORNEY March 1, 19 49. 3, w s w 2,463,210

DELAYED-ACTION FUSE Filed April 15, 1947 2 Sheets-Sheet 2 i F! 3 24\ v28- 30 23' 29 A ,W 4 N9. 9 ,2/ k "V ii 35 J 31 34 Q Fm. S-

I2 22 Q i l INVENIOR ATTORNEY Patented Mar. 1, 1949 UNE'FED STATESDELAYED-ACTION FUSE Application April 15, 1947, Serial No. 741,452

2 Claims.

The present invention relates to a delayed action fuse for militarymissiles; more particularly to a fuse for projectiles used in destroyingarmored and concrete structures.

An object of the invention is to provide a delayed action fuse for alltypes of military missiles.

Another object of the invention is to provide a fuse in which the firingpin is cocked upon impact and afterwards fires the primer when thenegative acceleration or deceleration of the projectile drops to aselected value as the missile is further retarded during penetration.

A further object of the invention is to provide a fuse which will permita projectile to penetrate a considerable thickness of armor or concretebefore the fuse explodes the bursting Charge within the projectile.

Among the advantages of this invention is the simple construction ofthis fuse over devices of the prior art. Moreover, deterioration instorage is reduced, inasmuch as none of its mechanical parts other thandetent springs, are under any strain prior to being fired and alsobecause the fuse is completely sealed against the elements.

The advantages of the present invention will be best understood inconnection with the accompanying drawings:

Fig. 1 is a detailed sectional view of a fuse embodying the inventiontaken through the axis of the fuse when in the unarmed condition.

Fig. 2 is a similar view of the fuse when the projectile is in flight.

Fig. 3 is a similar View of the fuse at the moment of impact of theprojectile on the target.

Fig. i is a similar view of the fuse at an infinitesimally later time.

Fig. 5 is a similar view of the fuse at the moment of firing the primer.

In the preferred embodiment of the invention, the cylindrical fuse bodyH has an axial bore l2 extending from the rear to the forward edges ofthe detents 53. The right or rear end of the bore I2 is tapped toreceive the primer holder 54 containing detonator or primer l5. Withinthe bore !2, the cylindrical firing pin it is housed in the cylindricalinertia sleeve l! in a slide fit and locked to this sleeve by a shearWire E8. The shear wire 18 passes through the holes IS] of the sleeveand 2?: of the firing pin, and each end of the wire is bent over in theannular groove 2i of the inertia sleeve El. The rear face of sleeve I?has a recess of greater diameter than the firing pin is to accommodatethe segmental split ring 22. The internal diameter of ring 22 is lessthan the diameter of firing pin l6, and the ring prevents the point 23of the firing pin from reaching the primer I5.

The forward end of the fuse body II has a stepped circular recess 24. Inthe narrower portion of this recess 24 is located a resilient, conicalBelleville washer 25 anchored in position by a retaining ring 25 whichfits into the stepped or wider portion of the recess 24. An interiorpartition or flange 2! with an aperture of the same diameter as theinterior of sleeve I1 separates recess 2s from the bore 12. Flange 21serves to limit the throw of the Belleville washer. A flanged guidebutton 28 is mounted in the center of the Belleville washer 25 and isequipped with a stud 29 projecting to the rear along the axis of thefuse. The stud 29 fits into a counter-sunk guide hole 38 in the forwardend of the firing pin it to maintain the pin in alignment. Two or moresafety detents l3 bear on the sides of the firing pin l6 in order toprevent the inertia sleeve I? from sliding forward prior to firing theprojectile from a gun. Detents l3 are slideably mounted on helicalsprings 35 in the detent cups 32 and channels 33 radially located in thefuse body II. The entire fuse assembly is inserted in a cylindricalmetal cover 34 which is open at one end. The open end is then crimpedover the rear base of the fuse body at 35.

Prior to a projectile being fired, the fuse is in the condition shown inFig. 1. Firing pin [6 and sleeve I! are locked together by shear wire I8. The point 23 of the firing pin I6 is prevented from approachingprimer 15 by the split ring 22. The Belleville washer 25 is in itsuncooked. position. Sleeve i? cannot move, as it bears against theprimer holder M at the rear and the detents l3 :at the forward end. Itis apparent that the fuse in the unarmed condition is absolutely safewith the firing pin separated from the primer by a split ring, locked bya shear Wire and having its driving member, in this case the Bellevillewasher, uncooked. The only working parts which are stressed in anydegree are the detent springs 3| which are under light compression intheir extended position.

In the operation of the fuse the projectile containing it is first firedfrom a gun. Under the influence of the high speeds of rotation caused bythe rifiing of the barrel, the detents l3 spin out, that is, they aremoved radially outward in the channels 33 and detent cups 32 as shown inFig. 2. During the flight of the projectile no other action occurs inthe fuse mechanism.

The condition of the fuse at the instant of the impact on a target isillustrated in Fig. 3. From the inertial forces resulting from thenegative acceleration, firing pm Hi and inertia sleeve 11 move forwardas a unit thereby flattening and cocking the resilient Belleville washer25. In cocking the washer, the mass of both the firing pin l6 and sleeveH is required to overcome the peak resisting force of the washer 25. Thefiring pin, Bellevillewasher and guide button reach the limit of theirtravel at this stage but the inertia sleeve only partially completes itstravel.

An infinitesimal fraction of a second later, the fuse attains thecondition disclosed in Fig. l. Due to inertia, sleeve ll continuesforward thereby shearing the shear wire H3. The segments of the splitring 22 are pushed out of the rear recess in the inertia sleeve byreaction against the relatively stationary firing pin 10. Sleeve l1slides down the bore l2 until it is stopped by flange 2i. Centrifugalforce drives the segments of the split -ring 22 outward against thewalls of bore I2 where the segments will not interfere in later movementof the firing pin. The fuse which was armed by rotation upon leaving thegun barrel has now been cocked by impact upon a target.

At the-moment of impact the negative acceleration (sometimes referred toas reverse setback) of the-projectile starts at a maximum value andsteadily decreases as the projectile penetrates the target and slowsdown due to the resistance encountered. The negative accelerationdecreases to a selected-value whereupon the inertial force of the firingpin [6 is no longer sufficient to hold the-Belleville washer 25 in thecocked position.

As is evident in Fig. 5, the flattened or cocked Washer returns to theconical shape shown in Fig.

-1-sharply driving the firing pin it to the rear ingthe fuse;- that is,by varying the weight of the firing pin and the inertia sleeve or byvarying -the-stiffness-f the Belleville washer, it is possible toregulate the depth of penetration in a given material at whichdetonation of the projectile will occur. While various materials may beemployed for the construction of this fuse, metal is preferred becauseof its strength. As an example, in designing a fuse which will be cockedat a negative acceleration of 2000 times that of gravity (2000 g) anddetonate the projectile when this negative acceleration drops to 1500times gravity 1500 g), a Belleville washer is selected which has a peakor cocking force of 19 pounds and a minimum holding force of 6 pounds, afiring pin weighing 0.004 pound, inertia sleeve Weighing 0.008 poundtogether with a copper shear wire having a shearing strength of morethan 5.5 pounds and less than 8.0 pounds. -With this assembly,upon'impact as in Fig. 3, the combined inertia force of the firing pinl6 and inertia sleeve I1 is 24- pounds which is ample to cock theBelleville Washer against a resistance of 19 pounds.

The forcesinvolved are calculated by the-equation F=ma where Frepresents force in pounds, m'represents mass in pounds and a representsacceleration in units ofgravity, Thus the firing pin weighing .004 poundmultiplied by2000 g "6 pounds.

eXerts a force of 8 pounds, and the sleeve with a mass of .008 poundtimes 2000 g exerts a force of 16 pounds, when the negative accelerationis 2000 times the acceleration of gravity.

The action shown in Fig. 4 is readily understood by recalling that theinertia sleeve is exerting a force of 16 pounds on a shear wire whichhasa shearing strength of between-U 5.6 and 8 pounds and thereforerequires: atotaliforce of 11 to 16 pounds to shear the wire at both endsof hole 20 in firing pin I 6.

In the stage illustrated in Fig. 5, the value of negative accelerationdrops below 1500 g and the firing pin, which by then is alone holdingthe washer cocked, will exert a force of less than Since this force isless than the designed minimum holding force of 6 pounds, the Bellevillewasher reacts and hurls the firing pin to the rear with a net force ofabout 13 pounds (19 pounds less the inertia force of approximately 6pounds which is exerted. by. the ifirin'gupin in a forward direction)The Bellevillewasher ofthe present -example has a total travel of..050'-*between' the relaxe'd ornormal position and the cooked position."A gap of .025" is used between the point 23 ofthe firing pin and theforward end of the primer fi. Accordingly, the firing pin travel is-in-excess' of .075"'and all travel in excess of'.050"""is--"overtravel. The firing pin derives suflicient'momentumtoaccomplish this overtravel and-also to-set off the primer from theforce applied'by the-Belle,- ville washer.

The fuse of' the invention, although'particularly intended for useagainstconcrete fortifications, may be used with equalsuccessagainststeel and other varieties ofarmor. In addition to'theparticular application shown for rotatinglprojectiles, in place of theradial detents, the fuse could be readily adapted for other typesofmilitary missiles of the non-rotatingkind by substituting an,- otherarming device. Fuses for. bombs,...mortar shells and rockets areobviously within thescope of the invention. Thus it is evident thatthedevice disclosed is capable of aw-ideevariety-of applicationsasa delayedaction fuse.

Accordingly, it is to be understoodswthatathe invention is limitedonlyby the-scope of athe-xappended claims and not to the preferred embodi'ement disclosed.

What is claimed is:

1. In a delayed-action fuse, az fusezrbodym rovided with a longitudinalboregarprimer at -the rear end of the-bore. a;firing'pin.assembledi;within and joined by a shear member to aninerti'a-sleeve located insidethe bore, asegmental ring'looateel in a recess. the rearend '-of-thesleeve a'nd adapted to separate the -fir-ing"' pi-n and -theprimer; asafety detent extending'radially into the bore to preventforward'movement of the-sleeve and displaceable by'centrifugal force,aresilient conical washer adjacent the-forward end of the firing pin andadapted" to be fiattened by a force' and maintained fiat bya lesserforce ,=-whereby-,upon rotation the detent" is. displaced from-' theworethereby arming the fuse, thereafter-uponimpact the inertia of saidfiring pin and sleeve assembly carries it forward to flattentheresilient washer with the'sleeve continuing forward 'to shear theshear member-and. displace the segmental 'ring from said'irecess:thereby. cocking the "fuse,'- and thereafter upon reductionof th/negative acceleration to a predetermined value the resilient washerresumes-its normal conical-shape -thereby driving the firing pin intocontact with the primer to detonate the fuse.

2. A fuse for a missile that spins when fired from an ordnance piece,and comprising a firing pin, a primer, spacing means holding said pinout of contact with said primer, a snap spring normally urging said pintoward said primer, locking means normally preventing movement of saidpin toward said spring, but releasing said pin due to centrifugal forcewhen the fuse spins, a slidable 10 turn motion of the firing pin intothe primer under the urging of the snap sprin under further negativeacceleration will be removed.

BEN W. SEWELL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,309,768 Newell July 15, 19191,385,610 Flam July 26, 1921 15 2,336,701 Rasmussen Dec. 14, 1943FOREIGN PATENTS- Number Country Date 188,377 Great Britain Nov, 6, 1922

